The present invention relates to a high-temperature Nixe2x80x94MH battery and a method for making the same.
The present Nixe2x80x94MH battery usually comprises a pair of electrodes composed of a Ni cathode of nickel hydroxide, an anode of hydrogen-storing alloy, and a separator, and KOH solution is used as electrolyte. The cathode is made by mixing an active material Ni (OH)2, an electroconductive agent, an adhesive agent and water to make a syrup, and filling the syrup into an alkali-resistance basic plate.
In the Nixe2x80x94MH battery adopting the cathode mentioned above, two reactions will take place on the cathode during charge, namely the following reaction (1) and reaction (2). The reaction (1) is the charging reaction of NI (OH)2 on the cathode; the reaction (2) is the oxygen-formation reaction. When the temperature arises, the electric potential of reaction (2) will decrease, which will decrease the electric potential difference between reaction (2) and reaction (1).
Ni(OH)2+OHxe2x88x92xe2x86x92NiOOH+H2O+exe2x88x92xe2x80x83xe2x80x83(1)
4OHxe2x88x92xe2x86x922H2O+O2+4 exe2x88x92xe2x80x83xe2x80x83(2)
The competition between the two reactions mentioned above results in low charging efficiency of the cathode mentioned above. At the temperature of 50xc2x0 C., the charging efficiency can only reach 50-60%, which severely influences the performance of battery at high temperatures.
Japanese patent 8-31448 disclosed a high-temperature battery and a method for making the same. According to this patent, CeO2, Ce(OH)3, Ce(OH)4, H2O, Nd2O3, and Nd(O H)3 were added into the Ni cathode material as additives to improve the charging efficiency of the cathode. For instance, at 45xc2x0 C., the charging efficiency of the battery can reach 80-90%. However, this improvement is not enough. Nowadays, the Nixe2x80x94MH battery has been used at high temperatures more and more common, and the Nixe2x80x94MH battery with higher high-temperature performance is required. The present invention is based on this.
One object of the present invention is to provide a Nixe2x80x94MH battery for using at high temperatures.
Another object of the present invention is to provide a method for making the Nixe2x80x94MH battery for using at high temperatures.
The present invention provides a high-temperature Nixe2x80x94MH battery, comprising a cathode plate made up of a base place and cathode substances adhering on the base plate, an anode plate made up of a base plate and anode substances adhering on the base plate, a separator, a steel housing, built-up covers, characterized in that: the said cathode base plate is selected from the base plates of foamed nickel, fiber nickel, and porous steel strip; the said cathode substances comprise an active material of spherical nickel hydroxide, an electroconductive agent, and adhesive and an additive; in which, the said electroconductive agent is at least one selected from the group consisting of nickel powder, carbon powder, acetylene black, graphite powder, cadmium powder, zinc powder, Coxe2x80x94Zn alloy powder, cobalt powder, CoO, Co2O3, Co(OH)2 and Co(OH)3; the said adhesive is at least one selected from the group consisting of PTFE, CMC MC and PVA; the said additive is selected from the titanium additives which can restrain the electric potential descent in the oxygen-formation reaction at the Ni cathode during the charging at a temperature over 40xc2x0 C.
The present invention also provides a method for making the high-temperature Nixe2x80x94MH battery as mentioned above, comprising the following steps:
(1) making a cathode plate: mixing nickel hydroxide, an electroconductive agent, a titanium additive, an adhesive and water together, stirring the resulting mixture homogeneously, filling the homogeneous mixture into a cathode base plate which has been welded with electrode terminals, baking to dry, roller-compacting it to a desired thickness to obtain a cathode plate;
(2) making an anode plate: mixing a hydrogen-storing alloy powder, an electroconductive agent, an adhesive and water together, stirring the resulting mixture homogeneously, filling the homogeneous mixture into an anode base plate which has been welded with electrode terminals, baking to dry, roller-compacting it to a desire thickness to obtain an anode plate;
(3) Selecting a proper separator, putting it between the cathode and the anode made above, pressing them together tightly, or convoluting into a cylinder, and then putting it into a quadrate or cylindrical steel housing;
(4) Welding electrodes, injecting an electrolyte solution and then sealing;
(5) Battery activating;
(6) Battery assembling.